Hospitals typically have devices in the hospital rooms for the patient to communicate with a device at a nurses' station. The hospital room device may include a microphone (or other type of transducer) to convert the patient's voice into electrical signals for transmission to a speaker at the nurses' station. The hospital room device also typically includes a speaker to receive electrical signals (converted from sounds generated at the nurses' station) and to convert the electrical signals back into sounds. Both the microphone and the speaker each usually have 2-wires to communicate so that the combination microphone/speaker device includes a total of 4-wires.
In order to determine whether a device in the system is receiving or sending a communication, the device (either the nurses' station device or the patient device) typically includes a VOX (Voice Operated eXchange) circuit. For example, if patient device includes both a microphone and a speaker (with 2-wires for each of the microphone and speaker), the patient device can itself determine whether it is receiving or sending a communication by sensing whether there is an input signal on the 2-wires for the microphone. While this type of system is workable, a need exists for a simpler system for patients to communicate with a nurses' station.